US5976935A - Method of fabricating an electrically erasable and programmable read-only memory (EEPROM) with improved quality for the tunneling oxide layer therein - Google Patents
Method of fabricating an electrically erasable and programmable read-only memory (EEPROM) with improved quality for the tunneling oxide layer therein Download PDFInfo
- Publication number
- US5976935A US5976935A US09/149,587 US14958798A US5976935A US 5976935 A US5976935 A US 5976935A US 14958798 A US14958798 A US 14958798A US 5976935 A US5976935 A US 5976935A
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- oxide layer
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- tunneling
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- eeprom
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- 230000005641 tunneling Effects 0.000 title claims abstract description 44
- 238000004519 manufacturing process Methods 0.000 title description 3
- 238000000034 method Methods 0.000 claims abstract description 44
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- WQJQOUPTWCFRMM-UHFFFAOYSA-N tungsten disilicide Chemical compound [Si]#[W]#[Si] WQJQOUPTWCFRMM-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910021342 tungsten silicide Inorganic materials 0.000 claims abstract description 9
- 239000000758 substrate Substances 0.000 claims description 32
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 21
- 229920005591 polysilicon Polymers 0.000 claims description 21
- 239000004065 semiconductor Substances 0.000 claims description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 5
- 235000012239 silicon dioxide Nutrition 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 5
- 230000015556 catabolic process Effects 0.000 abstract description 4
- 238000006731 degradation reaction Methods 0.000 abstract description 3
- WNUPENMBHHEARK-UHFFFAOYSA-N silicon tungsten Chemical compound [Si].[W] WNUPENMBHHEARK-UHFFFAOYSA-N 0.000 abstract description 3
- 229920002120 photoresistant polymer Polymers 0.000 description 7
- 238000005229 chemical vapour deposition Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 238000005468 ion implantation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/401—Multistep manufacturing processes
- H01L29/4011—Multistep manufacturing processes for data storage electrodes
- H01L29/40114—Multistep manufacturing processes for data storage electrodes the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
Definitions
- This invention relates to semiconductor fabrication technologies, and more particularly, to a method for fabricating an EEPROM (electrically erasable and programmable read-only memory) device with improved quality for the tunneling oxide layers therein.
- EEPROM electrically erasable and programmable read-only memory
- An EEPROM electrically erasable and programmable read-only memory, also abbreviated as E 2 PROM
- E 2 PROM electrically erasable and programmable read-only memory
- the EEPROM is more versatile in utilization than other types of ROMs.
- the data erasure and rewrite operation can be carried out one bit at a time.
- a conventional single-polysilicon EEPROM device is illustratively depicted in the following with reference to FIGS. 1A-1C.
- FIG. 1A shows the first step, in which a semiconductor substrate 10 is prepared.
- a field oxide layer 11 is then formed in a selected area.
- a first oxide layer 12 is subsequently formed over the entire top surface of the substrate 10 and the field oxide layer 11.
- the first oxide layer 12 is then selectively removed so as to form a tunneling window 13, exposing a selected area on the substrate 10.
- a second oxide layer 14 is formed over the entire top surface of the wafer, including the entire first oxide layer 12 and filling the tunneling window 13.
- FIG. 1B shows the subsequent step, in which a polysilicon layer 15 and a tungsten silicide (WSi) layer 16 are successively formed over the entire top surface of the wafer through, for example, two respective chemical-vapor deposition (CVD) processes.
- the polysilicon layer 15 and the WSi layer 16 are then selectively removed, allowing the remaining portions of these two layers 15 and 16 that are laid over the tunneling oxide layer 14b on one side of the field oxide layer 11 to serve as a floating gate 17, while the remaining portions of the same over the gate oxide layer 14a on the other side of the field oxide layer 11 serve as a gate 18.
- FIG. 1C shows the subsequent step, in which a high-voltage ion-implantation (HVI) process is performed on the wafer with the field oxide layer 11, the floating gate 17, and the gate 18 serving as a mask.
- a heat-treatment process is then performed on the wafer.
- impurity ions are implanted and driven into the unmasked portions of the substrate 10 to form a pair of source/drain regions 19 in the substrate 10 on both sides of the gate 18.
- the floating gate 17 is formed from a combination of the WSi layer 16 and the underlying polysilicon layer 15. Since the WSi layer 16 is customarily formed through CVD process, remnant fluorine (F) or chlorine (Cl) atoms can be left in the WSi layer 16. A bad consequence of this can occur when the WSi layer 16 is heated in the subsequent heat-treatment process used to drive ions into the source/drain regions, because stress can occur in the heated WSi and the remnant fluorine or chlorine atoms in the WSi layer 16 can be diffused into the tunneling oxide layer 14b. This turns the tunneling oxide layer 14b into a trapping center. During operation of the EEPROM device, the electric charges caught in the trapping center cause uneven and inconsistent electric fields in the tunneling oxide layer 14b, which easily causes breakdown in the tunneling oxide layer 14b. The reliability of the resultant EEPROM device is thus degraded.
- a new method for fabricating an EEPROM device includes the following steps:
- the foregoing method of invention is characterized in that the portion of the WSi layer that is directly laid above the tunneling oxide layer is removed.
- the degradation in the quality of the tunneling oxide layer that occurs in the prior art due to the forming of a trapping center therein can be prevented.
- the quality of the tunneling oxide layer is thus more controlled, allowing the resultant EEPROM to operate reliably with high performance.
- FIGS. 1A-1C are schematic sectional diagrams used to depict the steps involved in a conventional method for fabricating an EEPROM device.
- FIGS. 2A-2E are schematic sectional diagrams used to depict the steps involved in the method according to the invention for fabricating an EEPROM device.
- FIGS. 2A-2E are schematic sectional diagrams used to depict the steps involved in the method according to the invention for fabricating a single-polysilicon EEPROM device on a semiconductor substrate.
- the semiconductor substrate is a P-type silicon substrate, but it is to be noted that the semiconductor substrate can also be N-type and selected from various other kinds of semiconductor materials.
- FIG. 2A shows the first step, in which a semiconductor substrate 20 of a first semiconductor type, such as a P-type silicon substrate, is prepared. A field oxide layer 21 is then formed on a selected area. Subsequently, a first oxide layer 22, such as a layer of silicon dioxide, is formed through CVD process over the entire top surface of the substrate 20 and the field oxide layer 21. The first oxide layer 22 is then selectively removed so as to form a tunneling window 23 to expose a selected area on the substrate 20. Next, a second oxide layer 24, such as a layer of silicon dioxide, is formed through CVD process over the entire top surface of the wafer to a thickness of about 80 ⁇ (angstroms). The second oxide layer 24 covers the entire first oxide layer 22 and fills the tunneling window 23.
- a first oxide layer 22 such as a layer of silicon dioxide
- the part of the second oxide layer 24 that fills the tunneling window 23, indicated by the reference numeral 24a, serves as a tunneling oxide layer, all the other parts of the second oxide layer 24 and its underlying first oxide layer 22 serve in combination as a gate oxide layer, here collectively indicated by the reference numeral 25.
- FIG. 2B shows the subsequent step, in which a polysilicon layer 26 is formed over the entire top surface of the wafer.
- a layer of tungsten silicide (WSi) 27 is then formed over the entire polysilicon layer 26. Both the polysilicon layer 26 and the WSi layer 27 can be formed through CVD process.
- a photoresist layer 28 is formed over the entire WSi layer 27, and is then selectively removed to expose the area of the WSi layer 27 directly located above the tunneling oxide layer 24a.
- FIG. 2C shows the subsequent step, in which the photoresist layer 28 is used as a ask to perform an anisotropic etch-back process on the wafer, whereby the exposed portion of the WSi layer 27 that is unmasked by the photoresist layer 28 is etched away until the top surface of the polysilicon layer 26 is exposed.
- the photoresist layer 28 is removed.
- an optional screen oxide layer 29 is formed over the entire wafer, which covers all the exposed surfaces of the WSi layer 27 and the polysilicon layer 26, but still leaving an empty space in the hole left by the removed portion of the WSi layer 27.
- the adhesion of the WSi layer 27 to the polysilicon layer 26 is poor, and the screen oxide layer 29 can prevent the WSi layer 27 from peeling away from the polysilicon layer 26.
- the provision of the screen oxide layer 29 is elective.
- FIG. 2D shows the subsequent step, in which a photolithographic and etching process is performed on the wafer using a photoresist layer 30 as a mask, whereby selected portions of the screen oxide layer 29, the WSi layer 27, and the polysilicon layer 26 are removed.
- the combination of the remaining portions of the polysilicon layer 26 and WSi layer 27 that lie above the tunneling oxide layer 24a serves as a floating gate 31, while the combination of the remaining portions of the same that are laid on the other side of the field oxide layer 21 serves as a gate 32.
- HVI high-voltage ion-implantation
- FIG. 2E shows that after the HVI process is completed, the photoresist layer 30 is first removed, and then a heat-treatment process is performed on the wafer so as to drive those impurity ions in the substrate 20 into the areas 33 (FIG. 2D). Through this process, the areas 33 are formed into a pair of source/drain regions 34.
Abstract
Description
Claims (8)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
TW087111580A TW432536B (en) | 1998-07-16 | 1998-07-16 | Method of fabricating an electrically erasable and programmable read-only memory (EEPROM) with improved quality for the tunneling oxide layer therein |
TW87111580 | 1998-07-16 |
Publications (1)
Publication Number | Publication Date |
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US5976935A true US5976935A (en) | 1999-11-02 |
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Application Number | Title | Priority Date | Filing Date |
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US09/149,587 Expired - Lifetime US5976935A (en) | 1998-07-16 | 1998-09-08 | Method of fabricating an electrically erasable and programmable read-only memory (EEPROM) with improved quality for the tunneling oxide layer therein |
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US (1) | US5976935A (en) |
TW (1) | TW432536B (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6177315B1 (en) * | 1999-05-28 | 2001-01-23 | National Semiconductor Corporation | Method of fabricating a high density EEPROM array |
US6221717B1 (en) * | 1998-09-29 | 2001-04-24 | Stmicroelectronics S.R.L. | EEPROM memory cell comprising a selection transistor with threshold voltage adjusted by implantation, and related manufacturing process |
US6773987B1 (en) * | 2001-11-17 | 2004-08-10 | Altera Corporation | Method and apparatus for reducing charge loss in a nonvolatile memory cell |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4851361A (en) * | 1988-02-04 | 1989-07-25 | Atmel Corporation | Fabrication process for EEPROMS with high voltage transistors |
US5591658A (en) * | 1994-08-30 | 1997-01-07 | National Semiconductor Corporation | Method of fabricating integrated circuit chip containing EEPROM and capacitor |
US5637520A (en) * | 1993-02-11 | 1997-06-10 | Sgs-Thomson Microelectronics S.R.L. | Process for fabricating integrated devices including flash-EEPROM memories and transistors |
US5679970A (en) * | 1992-07-03 | 1997-10-21 | Commissariat A L'energie Atomique | Triple gate flash-type EEPROM memory and its production process |
US5714412A (en) * | 1996-12-02 | 1998-02-03 | Taiwan Semiconductor Manufacturing Company, Ltd | Multi-level, split-gate, flash memory cell and method of manufacture thereof |
US5793081A (en) * | 1994-03-25 | 1998-08-11 | Nippon Steel Corporation | Nonvolatile semiconductor storage device and method of manufacturing |
-
1998
- 1998-07-16 TW TW087111580A patent/TW432536B/en not_active IP Right Cessation
- 1998-09-08 US US09/149,587 patent/US5976935A/en not_active Expired - Lifetime
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4851361A (en) * | 1988-02-04 | 1989-07-25 | Atmel Corporation | Fabrication process for EEPROMS with high voltage transistors |
US5679970A (en) * | 1992-07-03 | 1997-10-21 | Commissariat A L'energie Atomique | Triple gate flash-type EEPROM memory and its production process |
US5637520A (en) * | 1993-02-11 | 1997-06-10 | Sgs-Thomson Microelectronics S.R.L. | Process for fabricating integrated devices including flash-EEPROM memories and transistors |
US5793081A (en) * | 1994-03-25 | 1998-08-11 | Nippon Steel Corporation | Nonvolatile semiconductor storage device and method of manufacturing |
US5591658A (en) * | 1994-08-30 | 1997-01-07 | National Semiconductor Corporation | Method of fabricating integrated circuit chip containing EEPROM and capacitor |
US5714412A (en) * | 1996-12-02 | 1998-02-03 | Taiwan Semiconductor Manufacturing Company, Ltd | Multi-level, split-gate, flash memory cell and method of manufacture thereof |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6221717B1 (en) * | 1998-09-29 | 2001-04-24 | Stmicroelectronics S.R.L. | EEPROM memory cell comprising a selection transistor with threshold voltage adjusted by implantation, and related manufacturing process |
US6177315B1 (en) * | 1999-05-28 | 2001-01-23 | National Semiconductor Corporation | Method of fabricating a high density EEPROM array |
US6773987B1 (en) * | 2001-11-17 | 2004-08-10 | Altera Corporation | Method and apparatus for reducing charge loss in a nonvolatile memory cell |
Also Published As
Publication number | Publication date |
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TW432536B (en) | 2001-05-01 |
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Owner name: UNITED SEMICONDUCTOR CORP., TAIWAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LIN, YING-JEN;KO, JOE;HONG, GARY;REEL/FRAME:009452/0745 Effective date: 19980803 |
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